Presently, flat panel displays such as Liquid Crystal Displays (LCDs), Organic Light Emitting Displays (OLEDs), and Plasma Light Emitting Displays (PLEDs) are being examined and may play a significant role in the future of display technology. In several of these display technologies, patterning of substrates with low viscosity solutions have started attracting attention and have presented several technology hurdles.
In one conventional technology, a subtractive technology is use to produce a pattern. In this technology a layer is deposited onto a substrate. The layer is patterned by one of several methods such as photoresist patterning where portions of the layer are exposed and other portions are covered. The substrate with the layer that is patterned with photoresist is then subjected to an etching technique which removes the exposed portions of the layer. While this technology works well in certain situations, it has a number of problems. For example, there are many steps in producing a defined pattern the layer which is associated with a high cost. Also, certain materials may not be compatible with this technology which also may add to the cost of building a product.
In another technology, ink-jet technology is used to pattern the substrate. Ink-jet technology uses a liquid material that is formed into droplets that are forced out of a nozzle. However, ink-jet technology also has several problems when forming patterns on substrates. First, if a thermal ink jet technology is used, the temperatures that are used may damage the material that is being deposited to form a pattern. Additionally, another problem is that ink jet technology forms droplets in the shape of tear drops and are not intended to from continuous patterns. For example, when the droplet is ejected from the nozzle and hits the substrate the droplet splatters, thus having small amounts of the droplet contaminating unintended parts of the substrate. Further, droplet placement on a substrate is susceptible to air currents.
In another technology, continuous-stream technology is used to form a pattern on a substrate. Continuous-stream technology uses a liquid that is forced out a nozzle to form a continuous stream that is applied to a substrate. However, continuous-stream technology also has several problems. For instance, when the continuous-stream is applied to the substrate to form a pattern, critical dimensions of the pattern are extremely difficult to control. This is typically a result of the liquid spreading out across the substrate in an uncontrolled manner. Without control of dimensions, smaller patterns and feature sizes are not possible which further retards the capability of making smaller devices. Additionally, with the spreading of the liquid across the substrate, other problems can occur such as media mixing, diffusion of the pattern, and the like. All of these problems significantly increase the cost of manufacture, as well as degrading the quality of the device being manufactured.
It can readily be see that conventional subtraction, ink-jet, and continuous-stream technologies have several disadvantages and problems. Therefore, a precision continuous-flow technique for making patterns on substrates that would control critical dimensions and curtail pattern diffusion would be highly desirable.